Effect of Different Compaction Methods on Bridge Pavement

In order to analyze the influence of different compaction methods on bridge deck vibration and bridge pavement compaction quality, the field test and laboratory test of oscillating compaction and vibrating compaction were carried out. The results demonstrated bridge deck vibration caused by the intrinsic exciting force of compactor contributed to vibrating compaction. On the pattern of oscillating compaction, the disturbance of bridge deck due to the exciting force of compactor is the main factor to induce bridge vibration. Furthermore, the vibration acceleration and amplitude in lateral, longitudinal and vertical direction, oscillating compaction are much smaller than that of vibrating compaction. Compared with vibrating compaction, the rolling efficiency of oscillating compaction is obviously higher and the final compaction degree also is much higher. Besides that, phenomenon of crushing the coarse aggregate is exists in the compaction construction, in which the effect of vibrating compaction on crushing the coarse aggregate is more obvious than oscillating compaction, and the range of crushing the coarse aggregate caused by vibratory compaction is larger than oscillating compaction.

Cold isostatic compaction of nano-size powders: Surface densification and dimensional asymmetry

Cold isostatic pressing (CIP) is often used in the compaction of nano-sized powders. For technological reasons, however, uniaxial pressing prior to CIP takes place. This paper reveals the first quantitative measurements of density gradients within and the asymmetric sintering response of nanoscale zirconia compacts formed by (i) simple uniaxial compaction and (ii) specific ratios of uniaxial and CIP pressure. We find that CIP forms an exterior “skin” of higher but variable surface density and decreases the width of the density distribution. It does not eliminate density gradients; nonuniform shrinkage still occurs during sintering. The high- and low-density zones (the moving and fixed ram ends, respectively) that form during uniaxial compaction are reversed during CIP. Considering both density distribution width and spring-back cracking, the “best” uniaxial-CIP pressure combination is 1–20 ksi for this particular powder and an L/D of 1.0. The greater final compaction of the low-density zone during CIP causes relatively large variations in final dimensions (nearly 400 microns) in spite of the smaller density distribution width. The usually neglected uniaxial pressing step has definite technological impacts on the production of nanostructured components via compaction.